[feature] Add CI workflow to build image and smoke-test MCP servers #14

Problem this solves
tests/fixtures exists but there's no documented way to run tests, no CI badge, and no automated check that the four MCP namespaces (r2__*, ghidra__*, shell__*, angr__*) actually respond after a build. The README documents multiple build-failure modes, suggesting builds break silently often.

Proposed solution
Add .github/workflows/ci.yml:

• docker compose build
• docker compose up -d
• Import a fixture binary, call one tool per namespace, assert non-error response
• docker compose down -v

Acceptance criteria

• CI runs on push/PR to main
• Fails if any namespace doesn't come up
• Badge added to README
• Document how to run the same suite locally

Affected component(s)

• Container / Dockerfile
• MCP gateway
• Ghidra bridge (bridge_mcp_ghidra.py)
• Shell server (shell-mcp.py)
• r2mcp / radare2 tools
• angr MCP
• Agents (.claude/agents/)
• CI / build
• Docs

Additional context
Relevant links, upstream issues, or prior discussion.